Various methods are used to synthesize aminoalcohols. However, they all suffer from the various drawbacks detailed below. The discussion of the various methods that are currently utilized to synthesize an aminoalcohol will utilize 3-dimethylamino-2,2-dimethyl-1-propanol (DMADMPOL) as an exemplary situation.
The first route known in the art is to reduce an ester or amide as is shown in the exemplary synthesis route shown below:
where LDA is lithium diisopropylamide [(CH3)2CH]2NLi. This synthesis route is not practical due to the low yield and high cost of lithium reagent used in the system (see, e.g., Madder et al., J. Chem. Sci., Perkin Trans. 1997, 2, p. 2787).
The second route known in the art is to reduce a corresponding aldehyde as is shown in the exemplary synthesis routes shown below:

The above routes involve the reduction of 3-dimethylamino-2,2-dimethyl-propanal with a reducing agent such as Na[Hg] (see, e.g., Mannich et al., Ber., 1932, 65, p, 378) or NaBH4 (see, e.g., Traynelis et al., J. J. Org. Chem., 1961, 26, pp. 686 to 691). These routes although possible, still require a large quantity of reducing agent in order to produce the desired aminoalcohol. Additionally, the yield on the first reduction route is too low to be practical.
A third route, which has been attempted, is to subject a corresponding aldehyde to hydrogenation with a catalyst as is shown in the exemplary synthesis route shown below:

However, various difficulties have been reported relating to the hydrogenation of this aldehyde shown above (see, e.g., W. Wenner, J. Org. Chem., 1950, 15, 2, pp. 301 to 304). As reported therein, the hydrogenation of DMADMPAL did not stop at the desired alcohol stage (see, e.g., W. Wenner, J. Org. Chem., 1950, 15, 2, pp. 301 to 304; Mannich et al., Ber., 1922, 55, pp. 356 to 365; and Mannich et al., Ber., 1932, 65, pp. 385 to 390).
It has also been reported that when hydrochloride salt of 3-dimethylamino-2,2-dimethyl-1-propanal (DMADMPAL) is hydrogenated with noble metal catalysts, only poor yields of the desired product 3-dimethylamino-2,2-dimethyl-1-propanol (DMADMPOL) are obtained. Part of the reason for such poor yields is that hydrogenolysis of the amine functional group is observed. Hydrogenation of the free amine gave even a worse result even though noble metal and nickel catalysts were tested (see, e.g., W. Wenner, J. Org. Chem., 1950, 15, 2, pp. 301 to 304). The hydrogenation of 3-dimethylamino-2,2-dimethyl-1-propanal (DMADMPAL) was finally achieved when the hydrochloride salt was employed in conjunction with Raney® Nickel as a catalyst (see, e.g., W. Wenner, J. Org. Chem., 1950, 15, 2, pp. 301 to 304 and U.S. Pat. No. 2,477,842). This process is also not cost efficient since protonation and deprotonation of the amine moiety of the aminoaldehyde added significant processing cost to the final product.
Regarding U.S. Pat. No. 2,477,842, this patent utilizes a method to convert an aminoaldehyde to an aminoalcohol that requires the use of an acid compound to convert the aminoaldehyde into a salt in order to achieve sufficient protonation of the amino group to permit the desired conversion. As would be apparent to those of skill in the art, the process of U.S. Pat. No. 2,477,842 is pH dependent and requires the use of a base compound at a later point to permit the reconversion of the salt compound to the desired aminoalcohol. Additional drawbacks of the process disclosed in U.S. Pat. No. 2,477,842 are: (i) the need to use at least stoichiometric amount (or even in excess of a stoichiometric amount) of acid to ensure complete protonation of the aminoaldehyde starting material to the necessary aminoaldehyde salt; and (ii) the need to use a stoichiometric amount (or even in excess of a stoichiometric amount) of base to neutralize the acid utilized in the reaction process and to permit the reconversion of the salt compound to the desired aminoalcohol.
Given the above, there is a need for a synthesis route for producing aminoalcohols from a suitable starting component (e.g., a free aminoaldehyde) that is both practical and permits the realization of suitably high yield without the need for the intermediate steps of protonating the amine moiety of the aminoaldehyde starting material and the subsequent deprotonation of the amine moiety of the aminoalcohol reaction product to recover the free aminoalcohol.